Backlight for touchless gesture detection

ABSTRACT

A device and method to detect a gesture performed by an object in touch-less communication with the device are described. The device includes two or more ambient light sensors arranged at respective first surface locations of the device, each of the two or more ambient light sensors sensing light intensity at the respective first surface location. The device also includes one or more processors to control one or more light sources at respective second surface locations of the device based on the light intensity sensed by the two or more ambient light sensors, calibrate the two or more ambient light sensors based on the one or more light sources, and detect the gesture based on the light intensity sensed by each of the two or more ambient light sensors.

BACKGROUND

Computers, mobile phones, tablets, and other computing and communication devices include a variety of input interfaces. For example, computers include keyboard and mouse input interfaces. Using a mouse, a user may navigate to an area of the display and make a selection. For various reasons, a mouse or equivalent input interface is not practical for handheld devices such as tablets and mobile phones. One of those reasons is that a handheld device is generally not used on a flat, stable surface to accommodate mouse operation. Most tablets and many mobile devices include capacitive touch sensors built under the screen that are used as a primary navigation and data input method. These touch sensors require users to navigate the display with their finger, thereby potentially obstructing the screen as they try to make a selection and leaving finger prints and smudges on the screen over time.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

FIG. 1 shows a device including an exemplary arrangement of ambient light sensors;

FIG. 2 depicts another view of the device shown in FIG. 1;

FIG. 3 shows a device including an exemplary arrangement of ambient light sensors according to another embodiment;

FIG. 4 shows a device including an exemplary arrangement of ambient light sensors according to yet another embodiment;

FIG. 5 is a block diagram of a system to process gestures;

FIG. 6 is a block diagram of a system to control the two or more ambient light sensors;

FIG. 7 shows the process flow of a method of detecting a gesture;

FIG. 8 is a block diagram of an exemplary device that facilitates touch-less gesture detection as described herein;

FIG. 9 shows an arrangement of backlight sources in an exemplary device according to an embodiment;

FIG. 10 is a block diagram of a system to control the backlight sources according to an embodiment; and

FIG. 11 is a process flow of an exemplary method of performing touch-less gesture detection under any ambient lighting conditions.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrative implementations of one or more embodiments of the present disclosure are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

As noted above, many input interfaces are available for computation and communication devices. Embodiments of the system and method described herein relate to touch-less gesture detection as a user interface. Additional embodiments relate to a light source and calibration based on the light source to facilitate the gesture detection.

FIG. 1 shows a device 100 including an exemplary arrangement of ambient light sensors 110. The device 100 may be any computation, communication, or data storage device such as a tablet, laptop computer, smart phone, music player, storage device, and the like. The view depicted by FIG. 1 shows the screen 120 (e.g., glass or other transparent surface) of the device 100 on a surface of the body 125 that displays information to a user, which can be based on user selections or generated by the device 100. Information generated by the device can include the status of communication connections (mobile network, wifi connection(s), Bluetooth connections, etc.), telephone call, or electronic messages or any combination thereof. The screen 120 can act as the input/output (I/O) between the device 100 and the user. The exemplary device 100 shown in FIG. 1 has a screen 120 that occupies most of one surface of the device 100. Other exemplary devices 100 may instead include a keyboard or other components such that the relative size of the screen 120 to the size of a surface of the device 100 is smaller than shown in FIG. 1 (see e.g., FIG. 4). Three ambient light sensors (ALSs) 110 x, 110 y, 110 z are disposed beneath the screen 120 in FIG. 1. Although the ALSs 110 are shown disposed beneath the screen 120 to protect from environmental and accidental damage, the ALSs 110 receive the same intensity of ambient light or at least sufficient ambient light to detect a change in ambient light whether they are disposed above or below the screen 120, because the screen 120 is a transparent device element that allows ambient light to pass through. The screen 120 includes a glass or polymer exterior layer that may filter or diffuse some light, e.g., certain ranges of light wavelengths. Sufficient light for detection as described herein passes through the exterior layer of the screen 120. The ambient light refers to the available light (brightness and direction of light) in the environment in which the device 100 is being used. As such, the ALSs 110 are passive devices. In an example, the ALSs 110 do not have and are not associated with emitters on the device 100 to provide the light that is detected by the ALSs 110. In a further example, the device 100 does not emit light for the purpose of gesture detection. Ambient light is, in an example, the light present in the environment in which the device is present.

FIG. 2 depicts another view of the device 100 shown in FIG. 1. The view shown by FIG. 2 includes a light source 210. This light source 210 may be the sun, a lamp, or some combination of light sources that provide the available light in a given environment in which the device 100 is being used. If the device 100 is outside during the day, the sun provides the ambient light, which is spread spectrum light. If the device is being used indoors with no exterior windows, the ambient light is generated by indoor lighting systems, e.g. lamps, fluorescent bulbs, incandescent bulbs, LEDs, etc. The ambient light can also be a combination of natural light (e.g., sunlight) and artificial light (e.g., fluorescent light, incandescent light). Each ALS 110 outputs a current level corresponding with the measured light intensity 115 (see e.g., FIG. 5). An analog-to-digital converter may be used to derive a digital output from the ALSs 110. Each of the ALSs 110 may have adjustable sensitivity (adjustable gain setting). Each ALS 110 may also be a spread spectrum sensor with a selectable range of operation among two or more ranges (wavelength bands or ranges). The process entailed in this selection is discussed further below with reference to FIG. 6. The full range of operation of each ALS 110 may be close to the wavelength range of visible light (400 nm to 700 nm). A typical commercially available ALS may detect ambient light in the wavelength range of 350 nm to 700 nm, for example. Because each ALS 110 measures the intensity of the available (ambient) light within its zone of reception (see e.g. 230 y and 230 y′ defining a zone of reception for ALS 110 y and 230 z and 230 z′ defining a zone of reception for ALS 110 z), the ALS 110 is a passive sensor that does not require a corresponding emitter or transmitter. The zone of reception is typically cone-shaped with the cone dimensions being determined by an angle of half sensitivity. FIG. 2 is a cross-sectional view of an exemplary zone of reception. Each ALS 110 may measure light intensity 115 within its zone of reception in a photometric unit (lux) to provide a measure of lumens per square-meters or in a radiometric unit (irradiance) to provide a measure of watts per square-meters. In the embodiment shown by FIGS. 1 and 2, the three ALSs 110 x, 110 y, 110 z are arranged in a triangular pattern. That is, at least one ALS 110 is offset or not linearly aligned with at least two other ALSs 110.

Through the inclusion of two or more ALSs 110 (e.g., three ALSs 110 x, 110 y, 110 z), the device 100 shown in FIGS. 1 and 2 facilitates detection of a gesture by an object 240 that changes the light intensity 115 (see e.g., FIG. 5) in the zone of detection of one or more of the ALSs 110 due to movement of the object 240. Through the inclusion of three or more ALSs 110 with at least three of the three of more ALSs 110 in a triangular pattern (see e.g., FIG. 1), movement of an object 240 may be discerned in three dimensions. As is further detailed below, a gesture is detected and identified based on the changes in light intensity 115 measured by each of the ALSs 110 at different time instants or measurement cycles due to the movement of the object 240. That is, each of the ALSs 110 measures light intensity 115 simultaneously with the other ALSs 110 at a given time instant or in sequence with the other ALSs 110 for a measurement cycle, and the comparison of light intensity 115 measurements for different time instants or measurement cycles is used to detect a gesture. For example, assuming that the ALSs 110 measure light intensity 115 simultaneously (or near-simultaneously), at the time instant illustrated by FIG. 2, the object 240 is positioned such that the light intensity 115 detected by ALS 110 z is affected but the light intensity 115 detected by ALSs 110 x and 110 y is unaffected by the object 240. Based on a direction of movement of the object 240, the light intensity 115 detected by different ones of the ALSs 110 x, 110 y, 110 z may be affected at different times instants by the position of the object 240. The object 240 may be a hand, one or more fingers, a wand or another non-transparent item that partially or completely blocks the passage of ambient light so that its position may be detected based on the effect on measured light intensity 115.

A touch-free gesture may mimic a swipe, also known as a flick, which can be a particular type of touch on a touch-sensitive display. The swipe or flick may begin at an origin point and continue to an end point, for example, a concluding end of the gesture. A gesture may be identified by attributes or characteristics of the gesture as discussed further below. These attributes may include the origin point (of detection by an ALS 110), the end point, the distance travelled by the object 240, the duration, the velocity, and the direction, for example. A gesture may be long or short in distance and/or duration. Two points of the gesture may be utilized to determine a direction of the gesture. A gesture may also include a hover. A hover may be non-movement of the object 240 at a location that is generally unchanged over a period of time.

In the arrangement of ALSs 110 shown in FIGS. 1 and 2, a minimum distance may be required among the ALSs 110 x, 110 y, and 110 z (e.g., distance 220 between ALSs 110 y and 110 z) in order to distinguish the movement of the object 240. This minimum distance may generally be on the order of 2 centimeters (cm). More specifically, the minimum distance between ALSs 110 is based on an expected size of the object 240 as one factor. For example, when an open hand is used as the object 240, a greater minimum distance may be required to distinguish a gesture than when one finger is used as the object 240. This is because the open hand would cover all three ALSs 110 x, 110 y, 110 z at more time instants such that a movement of the open hand could only be distinguished when the object 240 is at an edge of the set of ALSs 110 x, 110 y, 110 z. According to one or more embodiments, the ALSs 110 may be positioned at the corners or along the edges of the screen 120 and, thus, the screen 120 size may determine the distance between the ALSs 110. When an open hand is anticipated to be the object 240 used to perform a gesture, a minimum distance between ALSs 110 of 3.5 cm may be used. The increased distance between ALSs 110 facilitates distinguishing the gesture (e.g., direction, speed) more clearly, because all ALSs 110 will not be covered by the open hand object 240 for the majority of the gesture movement.

Another distance that must be considered is the distance between the object 240 and the ALS 110 (e.g., distance 250 between the object 240 and ALS 110 z). First, as FIG. 2 makes clear, the object 240 must be between the light source 210 and the ALSs 110 in order to be detected by one or more of the ALSs 110 based on the effect of the object 240 on light intensity 115 detected by one or more of the ALSs 110. While a minimum distance is generally not required between the object 240 and an ALS 110 (i.e. the object 240 may almost touch the screen 120 surface), the object 240 may generally be 2-3 cm away from the screen 120 while performing the gesture. When the object 240 is too close to the ALSs 110 (screen 120 surface), then some portion of the beginning or end of a gesture may not be detected. This is due to the fact that the width of the zone of reception of the ALSs 110 (as shown in the cross-sectional depiction of FIG. 2 by 230 y and 230 y′ and by 230 z and 230 z′, for example) is narrowest at the surface of the ALSs 110 and increases with increased distance from the ALSs. Thus, as is clear from FIG. 2, an object 240 that is closer in distance to an ALS 110 (screen 120 surface) must also be closer to a center of the ALS 110 (in the perpendicular dimension, along the screen 120) in order to enter the zone of reception of the ALS 110. By hovering the object 240 above a given ALS 110 and moving it farther away (reducing the object 240 effect and increasing light intensity 115 measurement) or closer together (increasing the object 240 effect and decreasing light intensity 115 measurement), a gesture analogous to a mouse click may be made. Thus, double-click and triple-click gestures may be added to available distinguishable gestures.

FIG. 3 shows a device 100 including an exemplary arrangement of ambient light sensors 110 according to another embodiment. The exemplary device 100 shown in FIG. 3 is similar to the device 100 shown in FIGS. 1 and 2 in that the screen 120 occupies most of one surface of the device 100. The device 100 shown in FIG. 3 includes seven ALSs 110 a, 110 b, 110 c, 110 d, 110 e, 110 f, 110 g arranged around the perimeter of the screen 120. As shown in FIG. 3, ALS 110 a is offset from a common axial line 111 of ALSs 110 b, 110 c, and 110 d and also a common axial line 111′ of ALSs 110 e, 110 f, and 110 g. In alternate embodiments, one or more of the ALSs 110 b, 110 c, and 110 d or the ALSs 110 e, 110 f, and 110 g may be disposed such that they are not linearly aligned with other ALSs 110 along 111 or 111′, respectively. For example, both ALS 110 c and ALS 110 f may be disposed closer to the center of the screen 120 and, thus, offset from the axial line 111 common to ALSs 110 b and 110 d and the axial line 111′ common to ALSs 110 e and 110 g, respectively. Increasing the number of ALSs 110 increases the number of gestures that may be detected by the device 100. For example, one waving gesture (movement of the object 240 from one side of the device 100 to the other) is illustrated by FIG. 3. Because of the number of ALSs 110 around the perimeter of the screen 120, other waving gestures, distinguishable from the waving gesture shown in FIG. 3, are also possible. The object 240 may move from ALSs 110 d and 110 e to ALS 110 a, for example, or from ALS 110 d to ALS 110 g. It bears noting that, if the ALSs 110 were clustered closer together and the object 240 is a hand, as shown in FIG. 3, fewer distinguishable gestures are possible than when the ALSs 110 are disposed, as shown.

FIG. 4 shows a device 100 including an exemplary arrangement of ambient light sensors 110 according to yet another embodiment. Unlike the exemplary devices 100 shown in FIGS. 1-3, the device 100 shown in FIG. 4 includes a keyboard or other component in the space 410 such that the screen 120 occupies less of one surface of the device 100 relative to the screen 120 shown in FIGS. 1-3. Three ALSs 110 m, 110 n, 110 o are shown near the perimeter of the screen 120. As noted above and shown in FIG. 1, the ALSs 110 m, 110 n, 110 o may be disposed closer together so that the gestures made by the object 240 are more analogous to gestures a user of a touchpad may make with a finger.

FIG. 5 is a block diagram of a system 500 to process gestures. Functions performed by the system 500 are discussed below with reference to specific components. However, in alternate embodiments, the system 500 may process gestures using one or more processors and one or more memory devices that serve more than one of the functions discussed herein. In addition, the same processors and memory devices that process gestures as discussed below may perform other functions within the device 100. For example, the processor to identify gestures may be one of several digital signal processors (DSPs 801, FIG. 8) generally available in a smart phone or tablet.

An input to the system 500 is the light intensity 115 measured from each of the ALSs 110. The measurements are received by a data collection engine 510, which includes both memory and processor functionalities. As the light intensity 115 measurement data is received from each of the ALSs 110, the data collection engine 510 outputs a frame of data 520 for each time instant. That is, each frame of data 520 includes the light intensity 115 measurement for every ALS 110 at a given time instant. While each frame of data 520 may generally be discussed as including the light intensity 115 measurement for each ALS 110 at an instant of time, the ALSs 110 may instead sample light intensity 115 in turn (rather than simultaneously) such that a frame of data 520 includes light intensity 115 measurements for a period of time for one cycle of the ALSs 110. A processor functioning as a gesture identifier 530 receives each frame of data 520. The gesture identifier 530 may operate according to one of several embodiments as discussed below.

In order to identify a movement of the object 240 as a particular (known) gesture, the gesture identifier 530 uses a comparison of light intensity 115 measurements of the ALSs 110, as discussed below, along with a comparison with a gesture template 537 stored in a template memory device 535. A dynamically adjusted minimum change in light intensity 115 may be set based on expected noise and errors. That is, a threshold percentage of change in detected light intensity 115 may be required before it is interpreted as a true variation in ambient light. Based on the light intensity 115 measurements among the ALSs 110 within a frame of data 520 (for a single time instant or measurement cycle), the gesture identifier 530 may ascertain a position of the object 240. For example, for a given frame of data 520, if the light intensity 115 measurements of ALSs 110 d and 110 f are higher (by a defined threshold) than the light intensity 115 measurement output by ALS 110 e, then the object 240 may be determined to be over the ALS 110 e and, thereby, blocking some of the light from the light source 210. Based on the light intensity 115 measurements among two or more frames of data 520 (two or more time instants or measurement cycles), the gesture identifier 530 may ascertain characteristics of the (movement) gesture such as a direction of the movement, speed of the movement, and whether the movement is accelerating or decelerating. For example, if the light intensity 115 measurements of ALSs 110 d and 110 f are higher (by a defined threshold) than the light intensity 115 measurement output by ALS 110 e in one frame of data 520 and the light intensity 115 measurement of ALS 110 e is higher (by a defined threshold) than the light intensity 115 measurements output by ALSs 110 d and 110 f in the next frame of data 520, the gesture identifier 530 may ascertain that the object 240 moved from a direction of the ALS 110 e toward a direction of the ALSs 110 d and 110 f. If the change in light intensity 115 measurements occurred over several frames of data 520, then the movement of the object 240 may be ascertained as being relatively slower than if the change occurred over the course of one frame of data 240. Based on the ascertained characteristics of the gesture, the gesture identifier 530 may identify the gesture among a set of known gestures based on the gesture template 537.

The gesture template 537 facilitates the association of a movement of the object 240 discerned by the gesture identifier 530 with a particular known gesture. The gesture template 537 may be regarded as a sample of ideal light intensity 115 measurement data corresponding with each known gesture. More specifically, the gesture template 537 may be regarded as providing the ideal relative light intensity 115 among the ALSs 110 or frames of data 520 or both for a given known gesture. Thus, by comparing the input light intensity 115 measurements (in the frames of data 520) or comparisons of light intensity measurements 115 with the ideal measurements in the gesture template 537, the gesture identifier 530 identifies the object 240 movement as a known gesture. This identification of the gesture may be done by a process of elimination of the known gestures in the gesture template 537. Thus, the gesture identifier 530 may identify the gesture using the gesture template 537, through a process of elimination of available known gestures, before the object 240 movement is complete. In this case, the gesture identifier 530 may continue to process frames of data 520 to verify the detected gesture or, in alternate embodiments, the gesture identifier 530 may stop processing additional frames of data 520 after identifying the gesture and wait for a trigger signal 540 discussed below. Each of the ALSs 110 may be programmable to provide 10, 20, 50, 10, 125, 15, 200 and 250 samples of light intensity 115 (frames of data 520) a second. The ALS 110 scanning rate is a factor in determining the speed at which a gesture may be made in order to be recognized. That is, when the ALSs 110 are sampling at a rate of 10 light intensity 115 samples per second, the fastest identifiable gesture is much slower than the fastest identifiable gesture that may be made when the ALSs 110 are sampling at a rate of 250 light intensity 115 samples per second. The ALSs 115 sampling at a rate of 10 frames of data 520 per second (10 light intensity 115 samples per second each) may translate to an object 240 travelling 10 cm in 1.5 seconds in order to be recognized and processed properly. The system 610 (FIG. 6) may dynamically calculate and adjust the scanning rate of the ALSs 110.

Another input to the gesture identifier 530 is one of the gesture libraries 555 stored in a gesture library storage 550. Each gesture library 555 is associated with an application, and the gesture identifier 530 selects the gesture library 555 associated with the application currently being executed by the device 100. A given gesture library 555 associated with a given application may not include every known gesture in the gesture template 537. Thus, based on the application currently being executed by the device 100, the gesture identifier 530 may narrow down the set of known gestures within the gesture template 537 to compare against the frames of data 520 output by the data collection engine 510 in order to identify the gesture. A gesture library 555 indicates an action output 560 corresponding with a set of gestures. Thus, when the gesture identifier 530 identifies a known gesture based on the movement of the object 240 and the gesture template 537, and the gesture identifier 530 finds that known gesture among the set of gestures in a gesture library 555 associated with the application currently being run by the device 100, then the gesture identifier 530 outputs the corresponding action output 560 stemming from the object 240 movement. The action output 560 of the gesture identifier 530 acts as a command to the application being executed. For example, when the application being executed is a document editing session, the gestures identified by the gesture identifier 530 may correspond with action outputs 560 such as “next page” (wave down), “previous page” (wave up), “zoom in” (bringing fingers together), and “zoom out” (spreading fingers apart). If the device 100 is currently not executing any application or if the application currently being executed by the device 100 does not have a gesture library 555 associated with it, then, even if the gesture identifier 530 uses the gesture template 537 to identify a known gesture based on the movement of the object 240, no action is taken by the gesture identifier 530 based on identifying the gesture. That is, there is no action output 560 corresponding with the identified gesture, because there is no gesture library 555 to look up.

According to one embodiment, the gesture identifier 530 may not use the gesture template 537 to identify a gesture when no application is being executed by the device 100 or when an application without an associated gesture library 555 is being executed by the device 100. According to another embodiment, the gesture identifier 530 may not begin to process any frames of data 520 before receiving a trigger signal 540. The trigger signal 540 is detailed below with reference to FIG. 6. According to another embodiment, the gesture identifier 530 may process an initial set of frames of data 520 and then not process another set of frames of data 520 needed to identify the gesture until the trigger signal 540 is received. For example, the gesture identifier 530 may process a particular number of frames of data 520 or a number of frames of data 520 representing a particular length of time (number of time instants) and then stop processing further frames of data 520 until the trigger signal 540 is received. According to yet another embodiment, the gesture identifier 530 may continually process frames of data 520 as they are output from the data collection engine 510.

Regardless of the behavior of the gesture identifier 530 based on the trigger signal 540, the lack of an associated gesture library 555, or the lack of an application being executed at all, the data collection engine 510 still outputs the frames of data 520. This is because the light intensity 115 measurements may be used for background functions such as adjustment of the screen 120 backlighting, for example, based on the detected ambient light, even if gesture detection is not to be performed. Some of these background functions are detailed below with reference to FIG. 6.

FIG. 6 is a block diagram of a system 610 to control the two or more ambient light sensors 110. As noted with reference to FIG. 5, the functions described for the system 610 may be performed by one or more processors and one or more memory devices, which may also perform other functions within the device 100. The system 610 may be regarded as a background processing system, because it may operate continuously to dynamically control the ALSs 110. The system 610 receives the light intensity 115 measurements output by the ALSs 110 to the data collection engine 510 as frames of data 520. In alternate embodiments, the ALSs 110 may directly output light intensity 115 measurements to the system 610 as well as to the data collection engine 510. The system 610 may also receive additional information 620. This additional information 620 may indicate, for example, whether the device 100 is currently executing an application and, if so, which application the device 100 is currently executing.

Based on the light intensity 115 measurements (directly or in the form of frames of data 520) and the additional information 620, the system 610 adjusts the sensitivity or wavelength band or range or both for each ALS 110. For example, based on the available light (measured ambient light intensity 115), the system 610 may change the wavelength range for the ALSs 110 via a control signal 630 from the system 610 to one or more of the ALSs 110. The change (adjustment of wavelength range) may ensure that the ALSs 110 are focused in the correct wavelength (frequency) band for the current conditions. As another example, based on a change in available light (e.g., based on switching a light on or off), the system 610 may change the sensitivity of the ALSs 110. Any order of switching lights produces a new range of change in light intensity 115 to which the ALSs 110 must adapt. For example, the range of change of light intensity 115 to which the ALSs 110 are sensitive may be 50-250 lux. In a darker environment (e.g., a conference room during a presentation) the range of change of light intensity 115 to which the ALSs 110 are sensitive may be 2-15 lux. The adjustment of the ALSs 110 through the control signal 630 may be done continuously, periodically, or based on a trigger event such as, for example, a change in the application being executed by the device 100. For example, sensitivity adjustment may be done automatically once for every 5 frames of data 520. The system 610 may also adjust the order and frequency of light intensity 115 measurements by the ALSs 110. For example, based on additional information 620 indicating that a particular application is being executed by the device 100, the system 610 may send control signals 630 to have the ALSs 110 collect light intensity 115 samples for each cycle (frame of data 520) in a particular order and with a particular frequency.

In addition to controlling the ALSs 110, the system 610 may provide the trigger signal 540 to the gesture identifier 530 (see FIG. 5). Because the system 610 monitors the light intensity 115 measurements in the frames of data 520 to fulfill the background functions described above, the system 610 may additionally identify trigger events that signal when gesture processing should be initiated by the gesture identifier 530 and output the trigger signal 540 accordingly. For example, the system 610 may output a trigger signal 540 to the gesture identifier 530 when it receives a frame of data 520 that indicates a change in light intensity 115 measured by one or more ALSs 110. The change in light intensity 115 measurement may indicate a start of a movement of an object 240 and, thus, the start of a gesture. In various embodiments, the change in measured light intensity 115 may be 10%+/−3% or higher before the system 610 outputs a trigger signal 540. In an embodiment, the change in measured light intensity 115 may be 20%+/−5% or higher before the system 610 outputs a trigger signal 540. In an embodiment, the change in measured light intensity may be 25%+/−5% or higher before the system 610 outputs a trigger signal 540.

FIG. 7 shows the process flow of a method 700 of detecting a gesture according to embodiments discussed above. At block 710, arranging two or more ALSs 110 under the screen 120 of a device 100 may be according to the embodiments shown in FIGS. 1, 3, and 4 or in alternate arrangements according to the guidelines discussed above. Obtaining light intensity 115 measurements from the ALSs 110 (block 720) may be in photometric or radiometric units as discussed above. Obtaining (receiving) the light intensity 115 measurements may also include dynamically controlling the ALSs 110 with the system 610 to modify the wavelength range or spectral sensitivity of each ALS 110, for example. As discussed with reference to FIG. 6, the control by the system 610 may be based on light intensity 115 measurements by the ALSs 110, for example. Determining what, if any, application is being executed by the device 100, at block 730, may be done by the gesture identifier 530 and may be part of the additional information 620 provided to the system 610. At block 740, the process includes storing a gesture library 555 associated with each application that may be operated using touch-less gestures in the gesture library storage 550. Selecting the gesture library 555 associated with the application being executed by the device 100 may be done by the gesture identifier 530 at block 750. Block 750 may also include the gesture identifier 530 determining that no gesture library 555 is applicable because the device 100 is not executing any application or is executing an application without an associated gesture library 555. At block 760, processing the light intensity 115 measurements and identifying a gesture involves the data collection engine 510 outputting the frames of data 520 and the gesture identifier 530 using a comparison of light intensity 115 measurements in addition to the gesture template 537. Block 760 may also include the system 610 sending a trigger signal 540 to the gesture identifier 530 to begin or continue the gesture processing. Block 760 may further include the gesture identifier 530 not identifying the gesture at all based on not having a gesture library 555 available. At block 770, outputting an action signal 560 corresponding with the gesture based on the gesture library 555 is done by the gesture identifier 530 as detailed above.

FIG. 8 is a block diagram of an exemplary device 100 that facilitates touch-less gesture detection as described in embodiments above. While various components of the device 100 are depicted, alternate embodiments of the device 100 may include a subset of the components shown or include additional components not shown in FIG. 8. The device 100 includes a DSP 801 and a memory 802. The DSP 801 and memory 802 may provide, in part or in whole, the functionality of the system 500 (FIG. 5). As shown, the device 100 may further include an antenna and front-end unit 803, a radio frequency (RF) transceiver 804, an analog baseband processing unit 805, a microphone 806, an earpiece speaker 807, a headset port 808, a bus 809, such as a system bus or an input/output (I/O) interface bus, a removable memory card 810, a universal serial bus (USB) port 811, an alert 812, a keypad 813, a short range wireless communication sub-system 814, a liquid crystal display (LCD) 815, which may include a touch sensitive surface, an LCD controller 816, a charge-coupled device (CCD) camera 817, a camera controller 818, and a global positioning system (GPS) sensor 819, and a power management module 820 operably coupled to a power storage unit, such as a battery 826. In various embodiments, the device 100 may include another kind of display that does not provide a touch sensitive screen. In one embodiment, the DSP 801 communicates directly with the memory 802 without passing through the input/output interface (“Bus”) 809.

In various embodiments, the DSP 801 or some other form of controller or central processing unit (CPU) operates to control the various components of the device 100 in accordance with embedded software or firmware stored in memory 802 or stored in memory contained within the DSP 801 itself. In addition to the embedded software or firmware, the DSP 801 may execute other applications stored in the memory 802 or made available via information media such as portable data storage media like the removable memory card 810 or via wired or wireless network communications. The application software may comprise a compiled set of machine-readable instructions that configure the DSP 801 to provide the desired functionality, or the application software may be high-level software instructions to be processed by an interpreter or compiler to indirectly configure the DSP 801.

The antenna and front-end unit 803 may be provided to convert between wireless signals and electrical signals, enabling the device 100 to send and receive information from a cellular network or some other available wireless communications network or from a peer device 100. In an embodiment, the antenna and front-end unit 803 may include multiple antennas to support beam forming and/or multiple input multiple output (MIMO) operations. As is known to those skilled in the art, MIMO operations may provide spatial diversity, which can be used to overcome difficult channel conditions or to increase channel throughput. Likewise, the antenna and front-end unit 803 may include antenna tuning or impedance matching components, RF power amplifiers, or low noise amplifiers.

In various embodiments, the RF transceiver 804 facilitates frequency shifting, converting received RF signals to baseband and converting baseband transmit signals to RF. In some descriptions a radio transceiver or RF transceiver may be understood to include other signal processing functionality such as modulation/demodulation, coding/decoding, interleaving/deinterleaving, spreading/despreading, inverse fast Fourier transforming (IFFT)/fast Fourier transforming (FFT), cyclic prefix appending/removal, and other signal processing functions. For the purposes of clarity, the description here separates the description of this signal processing from the RF and/or radio stage and conceptually allocates that signal processing to the analog baseband processing unit 805 or the DSP 801 or other central processing unit. In some embodiments, the RF Transceiver 804, portions of the antenna and front-end unit 803, and the analog base band processing unit 805 may be combined in one or more processing units and/or application specific integrated circuits (ASICs).

Note that, in this diagram, the radio access technology (RAT) RAT1 and RAT2 transceivers 821, 822, the IXRF 823, the IRSL 824 and Multi-RAT subsystem 825 are operably coupled to the RF transceiver 804 and analog baseband processing unit 805 and then also coupled to the antenna and front-end unit 803 via the RF transceiver 804. As there may be multiple RAT transceivers, there will typically be multiple antennas or front ends 803 or RF transceivers 804, one for each RAT or band of operation.

The analog baseband processing unit 805 may provide various analog processing of inputs and outputs for the RF transceivers 804 and the speech interfaces (806, 807, 808). For example, the analog baseband processing unit 805 receives inputs from the microphone 806 and the headset 808 and provides outputs to the earpiece 807 and the headset 808. To that end, the analog baseband processing unit 805 may have ports for connecting to the built-in microphone 806 and the earpiece speaker 807 that enable the device 100 to be used as a cell phone. The analog baseband processing unit 805 may further include a port for connecting to a headset or other hands-free microphone and speaker configuration. The analog baseband processing unit 805 may provide digital-to-analog conversion in one signal direction and analog-to-digital conversion in the opposing signal direction. In various embodiments, at least some of the functionality of the analog baseband processing unit 805 may be provided by digital processing components, for example by the DSP 801 or by other central processing units.

The DSP 801 may perform modulation/demodulation, coding/decoding, interleaving/deinterleaving, spreading/despreading, inverse fast Fourier transforming (IFFT)/fast Fourier transforming (FFT), cyclic prefix appending/removal, and other signal processing functions associated with wireless communications. In an embodiment, for example in a code division multiple access (CDMA) technology application, for a transmitter function the DSP 801 may perform modulation, coding, interleaving, and spreading, and for a receiver function the DSP 801 may perform despreading, deinterleaving, decoding, and demodulation. In another embodiment, for example in an orthogonal frequency division multiplex access (OFDMA) technology application, for the transmitter function the DSP 801 may perform modulation, coding, interleaving, inverse fast Fourier transforming, and cyclic prefix appending, and for a receiver function the DSP 801 may perform cyclic prefix removal, fast Fourier transforming, deinterleaving, decoding, and demodulation. In other wireless technology applications, yet other signal processing functions and combinations of signal processing functions may be performed by the DSP 801.

The DSP 801 may communicate with a wireless network via the analog baseband processing unit 805. In some embodiments, the communication may provide Internet connectivity, enabling a user to gain access to content on the Internet and to send and receive e-mail or text messages. The input/output interface (“Bus”) 809 interconnects the DSP 801 and various memories and interfaces. The memory 802 and the removable memory card 810 may provide software and data to configure the operation of the DSP 801. Among the interfaces may be the USB interface 811 and the short range wireless communication sub-system 814. The USB interface 811 may be used to charge the device 100 and may also enable the device 100 to function as a peripheral device to exchange information with a personal computer or other computer system. The short range wireless communication sub-system 814 may include an infrared port, a Bluetooth interface, an IEEE 802.11 compliant wireless interface, or any other short range wireless communication sub-system, which may enable the device to communicate wirelessly with other nearby client nodes and access nodes. The short-range wireless communication sub-system 814 may also include suitable RF Transceiver, Antenna and Front End subsystems.

The input/output interface (“Bus”) 809 may further connect the DSP 801 to the alert 812 that, when triggered, causes the device 100 to provide a notice to the user, for example, by ringing, playing a melody, or vibrating. The alert 812 may serve as a mechanism for alerting the user to any of various events such as an incoming call, a new text message, and an appointment reminder by silently vibrating, or by playing a specific pre-assigned melody for a particular caller.

The keypad 813 couples to the DSP 801 via the I/O interface (“Bus”) 809 to provide one mechanism for the user to make selections, enter information, and otherwise provide input to the device 100. The keypad 813 may be a full or reduced alphanumeric keyboard such as QWERTY, DVORAK, AZERTY and sequential types, or a traditional numeric keypad with alphabet letters associated with a telephone keypad. The input keys may likewise include a track wheel, track pad, an exit or escape key, a trackball, and other navigational or functional keys, which may be inwardly depressed to provide further input function. Another input mechanism may be the LCD 815, which may include touch screen capability and also display text and/or graphics to the user. The LCD controller 816 couples the DSP 801 to the LCD 815.

The CCD camera 817, if equipped, enables the device 100 to make digital pictures. The DSP 801 communicates with the CCD camera 817 via the camera controller 818. In another embodiment, a camera operating according to a technology other than Charge Coupled Device cameras may be employed. The GPS sensor 819 is coupled to the DSP 801 to decode global positioning system signals or other navigational signals, thereby enabling the device 100 to determine its position. The GPS sensor 819 may be coupled to an antenna and front end (not shown) suitable for its band of operation. Various other peripherals may also be included to provide additional functions, such as radio and television reception.

In various embodiments, device 100 comprises a first Radio Access Technology (RAT) transceiver 821 and a second RAT transceiver 822. As shown in FIG. 8, and described in greater detail herein, the RAT transceivers ‘1’ 821 and ‘2’ 822 are in turn coupled to a multi-RAT communications subsystem 825 by an Inter-RAT Supervisory Layer Module 824. In turn, the multi-RAT communications subsystem 825 is operably coupled to the Bus 809. Optionally, the respective radio protocol layers of the first Radio Access Technology (RAT) transceiver 821 and the second RAT transceiver 822 are operably coupled to one another through an Inter-RAT eXchange Function (IRXF) Module 823.

As noted above in the discussion of the system 610, the sensitivity of the ALSs 110 may be adjusted based on the available light. When the available light drops below a minimum threshold (e.g., the device 100 is in a completely dark room with no windows as an extreme example), embodiments of the device 100 described below supply the ambient light (backlight) in order to facilitate gesture detection. Calibration of the ALSs 110 based on the backlight is also detailed below.

FIG. 9 shows an arrangement of backlight sources 910 in an exemplary device 100 according to an embodiment of the invention. According to the embodiment shown in FIG. 9, the backlight sources 910 are under the screen 120 and each is arranged in proximity to an ALS 110. That is, backlight source 910 a is proximate to ALS 110 x, backlight source 910 b is proximate to ALS 110 y, and backlight source 910 c is proximate to ALS 110 z. Each backlight source 910 may be regarded as a sectional flashlight that provides ambient light at one section of the device 100 screen 120. A backlight source 910 may be on or off and additionally may have varying controllable levels of brightness according to different embodiments. Adjustment of the backlight sources 910 through a calibration process is detailed below. When the ambient light in the environment in which the device 100 is being used (as indicated by the light intensity 115 outputs of the ALSs 110) is above a threshold value representing the minimum acceptable ambient light level for gesture detection, the backlight sources 910 may not be operational at all. Because a low light intensity 115 indication from only one or less than all of the ALSs 110 is likely due to a localized issue (e.g., one of the ALSs 110 is covered), the light intensity 115 sensed by most or all of the ALSs 110 is used to determine when the overall ambient light has dropped below an acceptable level to facilitate gesture detection. When the ambient light falls below this minimum threshold, one or more of the backlight sources 910 may be turned on to maintain a range of operation of the ALSs 110 within limits that facilitate the gesture identifier 530 being able to match the light intensity 115 levels with those in the gesture template 537. All of the backlight sources 910 a, 910 b, 910 c shown in FIG. 9 need not necessarily be turned on based on the sensed ambient light being below the minimum threshold. Instead, only one or two of the backlight sources 910 a, 910 b, 910 c may be turned on. Also, in alternate embodiments to the one shown in FIG. 9, there may be a single backlight source 910 or multiple backlight sources 910 may be arranged in a way that does not correspond with the arrangement of ALSs 110. However, having each of the backlight sources 910 a, 910 b, 910 c proximate to each of the ALSs 110 x, 110 y, 110 z turned on facilitates accurately discerning direction of movement of an object 240. This is because having fewer than all of the backlight sources 910 a, 910 b, 910 c on can be thought of as creating a bias. That is, if only backlight sources 910 a and 910 b were turned on based on insufficient ambient light conditions, then ALS 110 z (because of backlight source 901 c being off) would sense lower light intensity 115 levels than ALSs 110 x and 110 y whether or not a gesture were being performed in front of ALS 110 z. In addition, having fewer than all of the backlight sources 910 a, 910 b, 910 c turned on in insufficient ambient lighting conditions may not bring the ALSs 110 x, 110 y, 110 z back to operation within an acceptable range.

When the ambient lighting conditions dictate that the backlight sources 910 are needed, a calibration is performed for the ALSs 110. An exemplary calibration is discussed with reference to Table 1 below.

TABLE 1 910a 910b 910c 110x 110y 110z 0 0 0  5 lux  5 lux  5 lux 1 0 0 18 lux 15 lux 15 lux 0 1 0 15 lux 18 lux 15 lux 0 0 1 15 lux 15 lux 18 lux 1 1 1 26 lux 26 lux 26 lux Table 1 indicates an on (“1”) or off (“0”) state for each backlight source 910 a, 910 b, 910 c shown in FIG. 9 along with the resulting light intensity 115 (in photometric units of lux) sensed by each of the ALSs 110 x, 110 y, 110 z. Thus, each row of the table represents a state of the backlight sources 910 for which ambient light 115 values are recorded. The backlight sources 910 are adjusted in intensity and duration to provide the light intensity 115 readings shown in Table 1. That is, through the adjustment of the backlight sources 910, the ALSs 110 are calibrated to provide the exemplary light intensity 115 values shown in Table 1 regardless of the level of ambient light from sources other than the backlight sources 910 (when the ambient light level is below the minimum threshold). Thus, the calibration process provides the relative difference in light intensity of the backlight sources 910 a, 910 b, 910 c needed and a time delay between each of the backlight sources 910 producing light and each of the ALSs 110 beginning sensing of light intensity 115. This information may also be used in the synchronization between ALSs 110 and backlight sources 910 discussed below. The backlight sources 910 are monitored during their operation (e.g., at a rate of 10 times per second in an exemplary embodiment) to adjust the brightness of each backlight source 910 as needed.

To address potential false alarms, caused by a temporary obstruction to the light source 210 for example, operation of the backlight sources 910 may not begin until the light intensity 115 measurements of all the ALSs 110 are below the minimum threshold value for a certain period of time. In this way, the backlight sources 910 are not likely to be activated based on either a momentary reduction in ambient light level below the minimum threshold or a gesture that includes blocking one or more of the ALSs 110 from the light source 210. A user preference may be selected to prevent the backlight sources 910 from being operated, as well. For example, a user who leaves the device 100 on while sleeping in a dark room will not be disturbed by the backlight sources 910 based on selecting a setting in the device 100. The backlight sources 910 may override the existing screen 120 backlight of a device 100 that facilitates reading the device 120 screen in a dark environment. Thus, during a slide presentation in a dark conference room, for example, if the user wishes to use touch-less gestures to control the slide navigation, he or she may disable the screen 120 backlight and enable the backlight sources 910 based on settings selected in the device 100. When the backlight sources 910 are operational (have been turned on due to ambient light level dropping below the minimum threshold) and the ambient light level then exceeds another threshold representing a maximum acceptable ambient light level for gesture detection, one or more of the backlight sources 910 may be turned off. This maximum threshold value may have to be exceeded for a certain period of time before any of the backlight sources 910 is turned off to ensure that the backlight sources 910 are not disabled based on a temporary flash. This period of time may be the same as or different from the period of time for which the ambient light level must be below the minimum threshold to initiate operation of the backlight sources 910. Based on the maximum threshold, the backlight sources 910 are not left operational after ambient light sources (210) external to the device 100 have begun to provide sufficient light for gesture detection. This may happen because the device 100 is moved to a more well-lit area or because a light source 210 is turned on or restored, for example. Phase synchronization between the ALSs 110 and the backlight sources 910 (matching a frequency of when the ALSs 110 sense light intensity 115 with a frequency of the backlight sources 910) ensures sufficient sensitivity of the ALSs 110 to detect movements that make up gestures.

FIG. 10 is a block diagram of a system 1000 to control the backlight sources 910 according to an embodiment. The system 1000 includes a processor 1010 that receives information about the light intensity 115 sensed by each of the ALSs 110. While the processor 1010 is shown as separate from those discussed above as being part of the device 100, the processor 1010 may be one or more of the processors discussed above. For example, because the data collection engine 510 receives the light intensity 115 measurements from the ALSs 110 and the system 610 receives frames of data 520 collected by the data collection engine 510, the processor 1010 may be part of or work in conjunction with the gesture identifier 530 processor or one or more processors of the system 610. The processor 1010 that controls the backlight sources 910 may also include other processors (e.g., DSP 801) of the device 100. The processor 1010 sends one or more control signals 1020 to one or more backlight sources 910 to affect their operation and to synchronize the backlight sources 910 with the ALSs 110 as discussed above. The synchronization may require the processor 1010 to work in conjunction with the system 610 that controls the ALSs 110. The processor 1010 controls the backlight sources 910 according to the minimum and maximum thresholds discussed above, and may operate the backlight sources 910 based on the minimum or maximum threshold being crossed for a certain period of time.

FIG. 11 is a process flow of an exemplary method 1100 of performing touch-less gesture detection under any ambient lighting conditions. At block 1110, monitoring the ambient light level may be done by the processor 1010. When the ambient light level is determined to be above a minimum threshold, performing gesture detection at block 1160 includes the processes detailed above with reference to FIGS. 5 and 6. When the ambient light level is determined to have fallen below a minimum threshold, operating the backlight sources 910 at block 1120 includes calibrating the ALSs 110 (block 1130) as discussed with reference to Table 1 above and synchronizing the ALSs 110 and backlight sources 910 (block 1140). Monitoring the backlight sources 910 at block 1150 includes monitoring, reporting (e.g., to the processor 1010), and adjusting the level of brightness of each backlight source 910 as needed. At any time (e.g., after performing gesture detection at block 1160), monitoring the ambient light level at block 1110 may indicate that the backlight sources 910 may be turned off. For example, the maximum threshold may be exceeded by the light intensity 115 outputs of the ALSs 110.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein. 

What is claimed is:
 1. A device to detect a gesture performed by an object in touch-less communication with the device, the device comprising: two or more ambient light sensors arranged at respective first surface locations of the device, each of the two or more ambient light sensors configured to sense light intensity at the respective first surface locations; one or more processors configured to: control two or more light sources at respective second surface locations of the device based on the light intensity sensed by the two or more ambient light sensors, calibrate the two or more ambient light sensors in response to an ambient light level falling below a minimum threshold level for a first duration when the two or more light sources are turned off, wherein the two or more ambient light sensors are initially calibrated to provide a first set of light intensity measurements while the two or more light sources are off; turn on each of the two or more light sources after calibrating the two or more ambient light sensors; and detect the gesture based on light intensity sensed by each of the two or more ambient light sensors when the two or more light sources are turned on.
 2. The device according to claim 1, wherein a number of the two or more ambient light sensors is equal to a number of the two or more light sources and each respective first surface location corresponds with one of the respective second surface locations such that the two or more ambient light sensors are proximate to the two or more light sources, respectively.
 3. The device according to claim 1, wherein, after the two or more light sensors are initially calibrated to provide the first set of light intensity measurements, the one or more processors calibrate the two or more ambient light sensors to provide additional sets of light intensity measurements by turning on each of the two or more light sources one at a time as each of the two or more ambient light sensors sense light intensity at the respective first surface locations.
 4. The device according to claim 3, wherein, after the two or more light sensors are calibrated to provide the additional sets of light intensity measurements, the one or more processors calibrate the two or more ambient light sensors to provide a final set of light intensity measurements by turning on each of the two or more light sources as each of the two or more light sensors sense light intensity at the respective first surface locations, and in turn, the one or more processors establish a phase synchronization between the two or more light sources and the two or more ambient light sensors based on the light intensity measurement sets provided from the calibration.
 5. The device according to claim 4, wherein the one or more processors cause one of the light sources to be turned off with each of the other light sources being turned on when light intensity sensed by one of the ambient light sensors exceeds a maximum threshold level for a second duration that is longer than the first duration.
 6. The device according to claim 4, wherein the one or more processors adjust the two or more ambient light sensors during the calibration to sense a specific light intensity regardless of a level of ambient light from sources other than the two or more light sources.
 7. The device according to claim 6, wherein the final set of light intensity measurements comprises a specific light intensity for each of the two or more ambient light sensors that is a same light intensity as one another.
 8. The device according to claim 6, wherein at least one of the additional sets of light intensity measurements comprises a specific light intensity for one of the two or more ambient light sensors that is a different light intensity than the specific light intensity for each of the other two or more ambient light sensors, wherein the specific light intensity for each of the other two or more ambient light sensors is identical.
 9. A method of detecting a gesture made by an object in touch-less communication with a device, the method comprising: sensing, using two or more ambient light sensors arranged at respective first surface locations of the device, light intensity at the respective first surface locations; controlling, using one or more processors, two or more light sources at respective second surface locations based on the light intensity sensed by the two or more ambient light sensors; turning off the two or more light sources when an ambient light level is above a minimum threshold level; calibrating, using the one or more processors, the two or more ambient light sensors in response to the ambient light level falling below the minimum threshold level for a first duration, wherein the two or more ambient light sensors are initially calibrated to provide a first set of light intensity measurements while the two or more light sources are off; turning on each of the two or more light sources after calibrating the two or more ambient light sensors; and detecting, using the one or more processors, the gesture based on light intensity sensed by each of the two or more ambient light sensors when the two or more light sources are turned on.
 10. The method according to claim 9, further comprising the one or more processors: responsive to initially calibrating the two or more ambient light sensors to provide the first set of light intensity measurements, calibrating the two or more ambient light sensors to provide additional sets of light intensity measurements by turning on each of the two or more light sources one at a time as each of the two or more ambient light sensors sense light intensity at the respective first surface locations.
 11. The method according to claim 10, wherein, responsive to calibrating the two or more light sensors to provide the additional sets of light intensity measurements, the method further comprises calibrating the two or more ambient light sensors to provide a final set of light intensity measurements by turning on each of the two or more light sources as each of the two or more light sensors sense light intensity at the respective first surface locations, and in turn, establishing a phase synchronization between the two or more light sources and the two or more ambient light sensors based on the light intensity measurement sets provided from the calibration.
 12. The method according to claim 11, wherein the one or more processors cause one of the light sources to be turned off with each of the other light sources being turned on when light intensity sensed by one of the ambient light sensors exceeds a maximum threshold level for a second duration that is longer than the first duration.
 13. The method according to claim 11, further comprising the one or more processors adjusting the two or more ambient light sensors during the calibration to sense a specific light intensity regardless of a level of ambient light from sources other than the two or more light sources.
 14. The method according to claim 13, wherein the final set of light intensity measurements comprises a specific light intensity for each of the two or more ambient light sensors that is a same light intensity as one another.
 15. The method according to claim 13, wherein at least one of the additional sets of light intensity measurements comprises a specific light intensity for one of the two or more ambient light sensors that is a different light intensity than the specific light intensity for each of the two or more ambient light sensors, wherein the specific light intensity for each of the other two or more ambient light sensors is identical. 